The present invention relates generally to generating an image of a region from reflected and scattered light at selected wavelengths to enhance the contrast of objects within the region. More specifically, the present invention relates to hyperspectral imaging systems.
The present invention is a technique for creating images at different wavelengths of light and also for detecting variations in the images created. It may be used, for example, to show variations that exist or occur in an image area such as temperature gradients, or to detect changes that occur in an image area such as the entry into, departure from, or presence or absence in the area of an object or matter. The image area may be a region of water, land, space or any region that contains matter or is void.
In a specific application, this invention has applications to detecting bioluminescence of certain organisms known to attach themselves to various objects. In another specific application, fluorescence spectra characteristic of toxic gases and other chemicals may be detected.
In one aspect of the invention, an acousto-optic tunable filter hyperspectral imaging system is moved across a region to collect a rapid series of images of the entire region. Each image represents the intensity of light reflected by matter in the region at a different wavelength. The acousto-optic tunable filter hyperspectral imaging system may include a platform for moving the acousto-optic tunable filter hyperspectral imaging system over successive Y-coordinates of a region in a direction substantially parallel to a direction of motion of the platform. The platform may be an aircraft or any other platform suitable establishing relative motion between the acousto-optic tunable filter hyperspectral imaging system and the region.
In another aspect of the invention, light is received from a region at successive X-coordinates. In this aspect, the acousto-optic tunable filter hyperspectral imaging system may include input optics for receiving light from the region and scanning optics for aiming the input optics at successive X-coordinates of a xe2x80x9cslicexe2x80x9d of the region in a direction substantially perpendicular to the direction of motion of the motion platform. Light received from the region by the input optics is collimated, and the collimated light is polarized by a linear polarizer. The collimator and the linear polarizer may be any device or combination of devices suitable for collimating and polarizing the light received from the region by the input optics. In one embodiment, the collimated and polarized light is directed to an acousto-optic tunable filter which images a portion of the light received from the region at a plurality of selected wavelengths.
In another aspect of the invention, the passband wavelengths of the acousto-optic tunable filter may be stepped in increments small enough to detect extremely small variations in color. The passband wavelengths of the acousto-optic tunable filter may then be stepped in small increments, e.g. on the order of five nanometers.
In a further aspect of the invention, the intensity of the light received from the region at a specific wavelength in a selected series of stepped wavelengths is recorded for image processing. An image recorder may be used to record the intensity of the light received from the acousto-optic tunable filter for each of the plurality of selected wavelengths.
In another aspect of the invention, the acousto-optic tunable filter hyperspectral imaging system may further include an illumination source for illuminating the region. The illumination source may be any device suitable for illuminating the entire region or a portion of the region that includes an area from which light is being received by the input optics. In one such embodiment, the illumination source may be a laser or an ultra-violet lamp.